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348
METALLTJKGY OF IRON AND STEEL,
first four tests, all of which are below .10 per cent, in silicon, and the last three, which are above .30 per cent.
TABLE XVII-D. Physical Properties of Low-Silicon and High-Silicon Steels.
	a "s	Composition.; percent.				1 a	I M		'          43 sS	?
	*					& ..M	a	..	ns	&
							*> S o	o	rf 4>	0
	*y					s&		•*^ •	gp,	fl4»
p. g	umber < group.					lastic li Sounds ach.	Itimate pounds square J	lastic TI per cen	S 01 d <3> bfid o a	eductio per cen
										
0	fe	SI.       C.	S.	P.	Mn.	S	P	W	m	«
1	4	.056      .170	.061	.058	.576	49106	69675	70.5	21.5	46.3
2	3	.402      .160	.050	.096	.493	64798	78863	69.5	18.0	33.9
The effect caused by elements other than silicon may be calculated, carbon being taken at 1000 pounds for .01 per cent., and phosphorus at 1000. The result is as follows:
Group II should be stronger than Group I. On account of phosphorus, 3.8X1000..........
Lbs. per sq. in. ...... 3800
Group SI should be weaker than Group I. On account ol carbon, 1X1000................
Net strengthening from constituents other than silicon. Strengthening from all constituents including silicon—
1000 2800
Strengthening due to .35 per cent, of silicon....................... 6388
Strengthening due to each ,01 per cent, of silicon.................   183
This signifies that .20 per cent, of silicon would give an increase in strength of 3700 pounds per square inch, which is less than would be given by .04 per cent, of carbon.
The influence of silicon upon the tensile strength is often confounded with that of carbon. It is well known that the addition of high-silicon pig-iron to a charge of low steel strengthens the metal more than a similar addition of ordinary pig-iron. But the fact is lost sight of that this silicon prevents the burning of carbon, both by the absorption of oxygen and by the deadening of the bath, so that the resultant metal is of higher carbon.
If the ordinary color method were reliable, this would be detected and proper credit given to it, but often an increment of .03 per cent, of carbon is not shown by analysis, so that its effect upon the strength, which will amount to 3000 pounds per square inch, will